SLAP (Superior Labrum Anterior-Posterior) is a term used to denote a specific type of injury to the shoulder joint. To understand how it occurs, it is best to first examine the anatomy of the shoulder joint. A cross-section view of the shoulder is seen on the right. The body parts in the graphics and their names in the text have been color-coded for easy reference.
The shoulder is a ball-and-socket type of joint and is anatomically referred to as the gleno-humeral joint, describing the two bony structures involved. The socket is the glenoid cavity, a cup-shaped piece of bone that juts out from a corner of the shoulder blade (scapula). The rim of the glenoid cavity is formed by cartilage called the labrum. The ball that fits into the socket is the head (upper part) of the humerus (arm bone).
The upper (superior) part of the labrum anchors one of the two tendons of the biceps muscle . The other biceps tendon is not involved in the shoulder joint but is instead attached in the front of the chest to the coracoid process, which is also an extension of the shoulder blade. (The biceps receives its name from the fact it has two upper attachments, making it the Bi-Ceps meaning two-heads.) The feature that makes SLAP possible is the way the upper biceps tendon hooks over the head of the humerus. If the arm is forcefully bent inward at the shoulder, the humerus acts as a lever and tears the biceps tendon and labrum cartilage from the glenoid cavity in a front-to-back (anterior-posterior) direction. And that is how the name SLAP is derived - Superior Labrum Anterior-Posterior or, in plain English, Upper Rim Front-Back.
Note: The material provided in this web page is educational in nature and not medical advice. It is meant neither for self-diagnosis nor as a treatment recommendation. If you are concerned about any condition you think you may have, CONSULT YOUR DOCTOR.